The Texans' Mario Williams, 49ers' Vernon Davis, Cowboys' Jason Witten and Browns' Joe Thomas (from left to right) pose for a photo in front of an Apache AH-64D helicopter on March 5. The four NFL All-Stars are participating in their first-ever USO tour, traveling to nine bases in eight days to visit troops serving in the Persian Gulf.

We spent Day 4 of the NFL-USO tour at Bagram Air Base in Afghanistan, which is the main hub for Operation Enduring Freedom, our military's mission in Afghanistan. Our group arrived at Bagram from Qatar via a C-130 military cargo plane.

Our day began early, and after breakfast we moved to the flight line where we visited the pilots who fly Apache attack helicopters. Next we moved on to the F-15 and F-16 fighters, where we saw several jets take-off and land. One of the most stunning aspects of Bagram is that the base is set in a valley surrounded by 360 degrees of snow capped mountains. To watch these planes take-off and land with the mountains in the background is quite a majestic sight.

The next stop for our group was sure to be one of the most significant and meaningful stops of the entire trip -- a visit to the Pat Tillman USO Center. This visit did not disappoint, as the Tillman Center was packed with troops for a meet-and-greet with the players. And of course, seeing the Tillman Center meant a tremendous amount to the players, knowing that the center is named for and dedicated to a member of the NFL fraternity who gave up his football career and made the ultimate sacrifice for his country.

Over 10,000 troops pass through the Tillman Center in a given month. More than 300 servicemen and women visited during the meet-and-greet with our players to receive an autograph, take a photo, and chat with the players.

Another stop on Day 4 was the hospital on base. This not only gave us a chance to meet with all the hospital workers, but also visit with the patients who had been brought in from the field for emergency treatment. This visit was a sobering one, as the players spoke with troops in the ICU who only two days earlier had lost limbs in IED attacks. Several of these patients considered themselves fortunate because some of their squad members did not survive the attacks.

The last stop of our day was at a secret Special Forces compound where we had dinner with a group of Green Berets. After dinner, the Green Berets gave us a tour of their compound and showed us some of their advanced vehicles and weaponry. Needless to say, it was an impressive place, and a very impressive group of people.